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Norway’s Halden reactor takes first step toward decommissioning
The government of Norway has granted the transfer of the Halden research reactor from the Institute for Energy Technology (IFE) to the state agency Norwegian Nuclear Decommissioning (NND). The 25-MWt Halden boiling water reactor operated from 1958 to 2018 and was used in the research of nuclear fuel, reactor internals, plant procedures and monitoring, and human factors.
Mitsuo Manaka
Nuclear Technology | Volume 143 | Number 3 | September 2003 | Pages 335-346
Technical Paper | Radioactive Waste Management and Disposal | doi.org/10.13182/NT03-A3421
Articles are hosted by Taylor and Francis Online.
Immediately after the geological disposal of high-level radioactive waste, the oxygen initially existing in the repository is expected to strongly affect the redox condition of the near field. The oxygen dissolves in the groundwater, is transported by diffusion through it, and is consumed by the oxidation of pyrite as an impurity in bentonite. To assess the influence of the oxygen, this study was conducted to estimate the diffusion of dissolved oxygen (DO) and the rate of pyrite oxidation by DO in compacted purified and crude sodium bentonites (SBs) in more detail than the Manaka et al. study. The effective diffusion coefficient (De) of DO in the compacted purified SB was measured in low ionic strength solution (carbonate buffered solution with pH ~ 9) using the electrochemical method. The empirical equation between De value of DO and dry density (0.5 × 103-1.8 × 103 kg m-3) of purified SB was obtained as follows:DeDOKunipia-F = 8.2 ± 1.5 × 10-10× exp(-2.6 ± 0.2 ×10-3,where DeDOKunipia-F is the De of DO in compacted purified SB (Kunipia F) (m2 s-1) and is the dry density of the SB (kg m-3).On the other hand, the De value of DO in the compacted crude SB was estimated using the relationship between De values of tritiated water in compacted purified and crude SBs. The empirical equation between the De value of DO and dry density (0.5 × 103-1.8 × 103 kg m-3) of crude SB was derived as follows:DeDOKunigel-V1 = 2.04 × 10-9 exp(-2.6 × 10-3),where DeDOKunigel-V1 is the De of DO in compacted crude SB (Kunigel V1) (m2 s-1) and is the dry density of the SB (kg m-3).The rates of pyrite oxidation by DO were estimated from the experimental data in pyrite-purified SB systems using the obtained De values of DO. The relation between rate constant (k') of pyrite oxidation by DO and dry density () of the SB was derived as follows:k' = 3.9 ± 1.1 × 10-8 exp(-1.3 ± 0.3 × 10-3),where k' is the rate constant at pH ~ 9 in compacted purified SB of dry density ranging from 0.8 × 103 to 1.2 × 103 kg m-3.The rate constants of pyrite oxidation by DO in the compacted crude SB (0.8 × 103 to 1.2 × 103 kg m-3) were also calculated using the estimated De values of DO. In general, the values of rate constants in the crude SB are 1.5 times as large as that in the purified SB.
